Inhibition of Ca2+-signal-dependent growth regulation by radicicol in budding yeast

Compelled activation of Ca2+ signaling by exposure of zds1 Delta strain Saccharomyces cerevisiae cells to external CaCl2 leads to characteristic physiological consequences such as growth inhibition in the G(2) phase and polarized bud growth. Screening of microbial metabolites for activity alleviating the deleterious physiological effects of external CaCl2 identified the Hsp90 inhibitor radicicol as an inhibitor of Ca2+-signal-dependent cell-cycle regulation in yeast. Radicicol alleviated analogous physiological effects due to the expression of, a constitutively active form of calcineurin or overexpression of Swel, the negative regulatory kinase of the Cdc28-Clb complex. Western blot analysis indicated that radicicol inhibited Ca2+-induced accumulation of Swel and Cln(2).